BN Ch.26 The Digestive System

Question 1

On a chart, trace the digestive pathway, naming major organs of the gastrointestinal (GI) system and the function of each.

Answer 1

• Mouth
  
  • Chews and mixes food with saliva
• Pharynx
  
  • Directs food from mouth to esophagus
• Salivary glands
  
  • Secrete saliva
• Epiglottis
  
  • Protects airways during swallowing
• Trachea
  
  • Allows air to pass to and from lungs
• Esophagus
  
  • Passes food from the mouth to the stomach
• Esophageal sphincters
  
  • Allow the passage from mouth to esophagus and from esophagus to stomach, prevent back flow from stomach to esophagus and from esophagus to mouth
• Diaphragm
  
  • Separates the abdomen from the thoracic activity
• Stomach
  
  • Churns, mixes, and grinds food to a liquid mass
  • Adds acid, enzymes, and fluid pyloric sphincter
  • Allows passage from stomach to small intestine
  • Prevents back flow from small intestine
• Liver
  
  • Manufactures bile salts, detergent
  • Like substances, to help digest fats
• Gallbladder
  
  • Stores bile until needed
• Bile Duct
  
  • Conducts bile from the gallbladder to the small intestine
• Appendix
  
  • House bacteria and lymph cells
• Small intestine
  
  • Secretes enzymes that digest all energy
  • Yielding nutrients to smaller nutrient particles
  • Cells of wall absorb nutrients into blood and lymph ileocecal valve (sphincter)
  • Allows passage from small to large intestine prevents back flow from large intestine
• Pancreas
  
  • Manufactures enzymes to digest all energy
  • Yielding nutrients and releases bicarbonate to neutralize acid chyme that enters the small intestine
• Pancreatic duct
  
  • Conducts pancreatic juice from the pancreas to the small intestine
• Large intestine
  
  • Absorbs water and minerals; passes waste along with water to rectum
• Rectum
  
  • Stores water prior to elimination anus
  • Holds rectum closed; opens to allow elimination

Question 2

Define the following terms and processes: mastication, deglutition, and peristalsis.

Answer 2

• Mastication
  
  • Their chief function is to break food into smaller particles, accomplished through mastication, chewing.
• Deglutition
  
  • Voluntary movement of the tongue begins the swallowing process ( deglutition ), by lifting and pushing the bolus of food, mixed with saliva, into the pharynx, the next portion of the digestive tube.
  • The upper surface of the tongue appears rough because of visible indentations ( fissures ) and projections ( papillae ).
  • The taste buds are microscopic nipple-like projections located on the sides of the papillae.
  • They are specialized nerve endings allowing detection of various flavors, such as salty, bitter, sweet, sour, alkaline, and metallic.
  • The ability to taste food also depends on the sense of smell.
• Peristalsis
  
  • The smooth (involuntary) muscles pass food through the entire GI tube by waves of contractions, peristalsis , an alternating muscular relaxation and contraction, without which digestion cannot occur.

Question 3

Explain the actions of hydrochloric acid (HCl), gastrin, intrinsic factor, cholecystokinin, and pancreatic juice in the process of digestion.

Answer 3

• Hydrochloric acid (HCl)
  
  • Destroys microorganisms
• Gastrin
  
  • Stimulates secretion of gastric acid (HCl) and pepsin
• Intrinsic factor
  
  • Needed for absorption of vitamin B 12 , needed for development of RBCs (also requires folate)
• Cholecystokinin
  
  • Activates gallbladder to release bile
• Pancreatic juice
  
  • Breaks fats into tiny droplets (emulsification)

Question 4

Explain two functions of the pancreas and gallbladder as they relate to digestion.

Answer 4

• Gallbladder
  
  • Its major functions are storage and release of bile, as needed in the small intestine for fat emulsification.
  • It also concentrates bile by absorbing water and salts.
• Pancreas
  
  • As an endocrine gland, it secretes the hormones insulin, glucagon, and somatostatin into the bloodstream, to help regulate blood sugar levels.
  • Its exocrine function is to produce pancreatic juice, which is necessary for life, because it is vital in digestion.
  • It is produced by the acinar cells.
  • The acinar cells secrete three main enzymes that assist in digestion of specific nutrients:
    
    • Pancreatic amylase:
      
      • Starch/Carbohydrates
    • Trypsin:
      
      • Protein
    • Pancreatic lipase:
    • Fats, Lipids (into triglycerides)

Question 5

Describe the functions of the liver related to digestion.

Answer 5

• Only the brain is capable of more functions than the liver.
• Some of the liver’s major functions include the following:
  
  • Secretion of bile Absorption of bilirubin after destruction of old red blood cells (RBCs)
  • Detoxification of blood (removal of toxins or poisons)
  • Storage of fat-soluble vitamins (A, D, E, K)
  • Formation of vitamin A and some nonessential amino acids
  • Storage of vitamin B complex and iron
  • Formation of plasma proteins (albumin, prothrombin, globulins)
  • Synthesis of urea, a waste product from protein anabolism
  • Storage of glucose as glycogen (helps regulate glucose levels)
  • Synthesis of clotting factors (fibrinogen; prothrombin; factors V, VII, IX, X)
  • Formation of triglycerides and cholesterol
  • Secretion of heparin (anticoagulant)
  • Synthesis of immunoglobulins
  • Breaking down of fats (lipids)
  • Metabolism of carbohydrates; storage of fats and carbohydrates
  • Regulation of amino acids
  • Production of body heat
  • Storage of minerals
  • Production of lymph

Question 6

Describe the physiology of digestion and absorption, including how carbohydrates, fats, and proteins are broken down; describe absorption in the small intestine.

Answer 6

• Mechanical digestion
  
  • is the physical breakdown of food caused by chewing and the movement of food in the digestive tract.
  • Breaking food into smaller pieces exposes more food surface area to the effects of enzymes, acids, and other chemicals.
• Chemical digestion
  
  • is the breakdown of chemical bonds in food, with the addition of enzymes, acids, and water.
  • Some digestive processes begin in the mouth, pharynx, and stomach, but most digestion occurs in the duodenum.
• Chief cells .
  
  • Pepsinogen is a precursor of pepsin, the enzyme needed to break down proteins.
  • Gastric lipase breaks down triglycerides in butterfat (found in milk and dairy products).
  • Secrete pepsinogen and gastric lipase
• Parietal cells
  
  • Secrete hydrochloric acid (HCl), which functions to activate pepsinogen and kill most stomach microorganisms.
  • When activated, pepsinogen changes into the enzyme pepsin, which begins to break down proteins.
• Digestion of starches into glucose molecules starts in the mouth, but primarily takes place in the small intestine by the action of specific enzymes secreted from the pancreatic amylase: starch/carbohydrates
• Absorption in the Small Intestine
  
  • Absorption of approximately 85% of nutrients used by the body occurs across the villi , small finger-like projections on the mucosa of the small intestine, into the capillary network.
  • To increase surface area, villi contain microvilli, microscopic folds on the surface of epithelial cells in the cell membrane. (Unfolded and straightened out, one person’s villi and microvilli could completely cover more than 2,000 square feet, half a basketball court.)
  • Villi wave to keep food molecules thoroughly mixed with digestive juices.
  • Amino acids are absorbed in the duodenum and jejunum;
  • Most fats are absorbed in the jejunum.
  • Because villi are so important in absorption, they are heavily supplied with capillaries, which carry nutrients, via hepatic portal circulation, to the liver for further processing.
  • Active and passive transport are the means by which nutrients are absorbed into the circulation and then to the body’s cells.
  • Absorption of nutrients into the bloodstream occurs via the small intestine.
  • The body cannot use these food materials, however, until the bloodstream delivers them to the cells by transporting the particles across each cell’s membrane.

Question 7

Identify and describe two major categories of metabolism.

Answer 7

• Catabolism (destruction, catabolic phase)
  
  • Is the breakdown of larger molecules into smaller ones, releasing energy.
  • Cellular respiration is a series of catabolic reactions.
  • Catabolism (destructive metabolism): breaking down foods into useable substances (generates heat, carbon dioxide, water, and ATP)
  • The end products of catabolism resulting from cellular respiration are:
    
    • Carbon dioxide
    • Water
    • Energy
• Anabolism (construction, anabolic phase)
  
  • Is the synthesis of simpler substances into new, organized substances to be used by body cells.
  • Anabolism (constructive metabolism): using products of catabolism to build and repair body cells and maintain life
  • Examples of anabolism include synthesis of glycogen, triglycerides, or proteins.

Question 8

Explain how the large intestine changes its contents into fecal material.

Answer 8

• Whatever nutrients are not reabsorbed and sent to the portal (liver) circulation are eliminated as solid intestinal wastes ( defecation , bowel movement, egestion ).
• After water reabsorption, a plant fiber, cellulose, other undigested material, living and dead bacteria, and mucus remain.
• These mass together and pass into the rectum as solid or semisolid waste or feces (excrement, excreta), where they stimulate sensory nerve endings, causing a sensation of accumulating bulk and initiate the defecation (evacuation) reflex.
• Peristaltic waves push feces against the anal muscle as a signal for emptying the rectum (the defecation reflex ), and parasympathetic-controlled nervous activity causes strong contractions.
• The internal sphincter relaxes and pressure from peristalsis, along with pressure consciously exerted by the diaphragm and abdominal muscles, brings about defecation.
• To expel feces, the external anal sphincter, a skeletal muscle, relaxes voluntarily. If the defecation reflex is ignored routinely, the impulse tends to die and constipation often occurs.
• This can become life threatening if it results in bowel obstruction.

Question 9

List the effects of aging on the digestive system.

Answer 9

• Saliva production decreases
• Decreased Gag Reflex
• Bony structures decrease around the mouth
• Loss of teeth
• Taste decreases, especially sweet and sour tastes.
• Sense of smell decreases
• Gastric mucosa atrophies and secretions such as HCl, intrinsic factor, and enzymes may decrease
• Food stays in stomach longer
• Peristalsis decreases
• Reduced secretion of digestive juices
• Ignoring the need to defecate
• Occurrence of gallstones may increase
• Lower tolerance to some foods
• Ignoring hunger or thirst
• Decreases in absorptive surfaces in intestines, due to decreased villi height and decreased intestinal motility
• Fat tissue replaces muscle tissue
• Reduced exercise; poor diet
• Caloric needs decrease
• Physical inactivity
• Difficulty swallowing (may be due to disease process such as stroke, Huntington disease, etc.)
• Dementia—may forget to eat or may repeats meals
• Financial factors—cannot afford nutritious diet
• Unable to properly prepare foods
• Anal sphincter insufficiency

Question 10

The system of passageways for the transport of bile from the liver to the gallbladder to the intestine is known as __________ apparatus.

Answer 10

Biliary

Question 11

_________ digestion is the breakdown of
chemical bonds in food with the addition of
enzymes, acids, and water.

Answer 11

Chemical

Question 12

__________cells in the stomach mucosa secrete pepsinogen (breakdown proteins) and gastric lipase.

Answer 12

Chief

Question 13

A small, finger-like projection of the cecum is the vermiform _________.

Answer 13

Appendix

Question 14

In the stomach, all foods mix with gastric
juices and churn until they are in a
semiliquid form called __________.

Answer 14

Chyme

Question 15

The contraction of this organ results in continuation of the act of swallowing and pushes the food into the esophagus.

Answer 15

Pharynx

Question 16

Its secretion helps in the moistening of the food, making it eaiser to swallow, and in preventing oral infections.

Answer 16

Salivary Gland

Question 17

Within this organ, food is mixed with gastric juices and churned until it is in a semiliquid form called chyme.

Answer 17

Stomach

Question 18

It senses the temperature and is also involved with the mixing of the food with saliva.

Answer 18

Tongue

Question 19

Write the correct sequence of the steps involved in digestion in the boxes provided below.
1. The process of churning the food takes place in the pylorus of the stomach.
2. Absorption of the dissolved molecules occurs in the small intestine. The molecules are then taken into circulation.
3. The physical breakdown of food is
accomplished by the process of mastication.
4. Chemical breakdown of food occurs by the release of various enzymes.
5. Dilution of the food entering the digestive tract is accomplished by water and various enzymes.

Answer 19

3. The physical breakdown of food is
   accomplished by the process of mastication.
4. The process of churning the food takes place in the pylorus of the stomach.
5. Chemical breakdown of food occurs by the release of various enzymes.
6. Dilution of the food entering the digestive tract is accomplished by water and various enzymes.
7. Absorption of the dissolved molecules occurs in the small intestine. The molecules are then taken into circulation.

Question 20

Define metabolism. What is the difference

between basal metabolism, catabolism, and
anabolism?

Answer 20

• Metabolism is defined as the sum total of all the changes, both physical and chemical, that occur within the body.
  
  • Chewing and breaking down of food into smaller particles forms the physical conversions.
  • Chemical conversions involve the conversion of larger food particles into smaller ones by the action of enzymes.
• Its two components are catabolism and anabolism.
  
  • The amount of energy used by the body at rest is called as basal metabolism.
  • This is the amount that the body needs to sustain life.
• Catabolism (destruction, catabolic phase)
  
  • Is the breakdown of larger molecules into smaller ones, releasing energy.

Question 21

Describe the digestive process that takes place in the stomach.

Answer 21

• In the stomach, both mechanical and chemical digestion takes place.
  
  • Churning and mixing of the food occur here.
  • Continuation of the starch digestion occurs by ptyalin in the saliva from the oral cavity.
  • Continuation of the fat digestion by lingual lipase also occurs.
• Protein digestion is started in the stomach by pepsin.
  
  • However, these processes are not completed within the stomach.
• The presence of intrinsic factor helps in the absorption of vitamin B12.

Question 22

A nurse is undertaking a general assessment
of a 3-year-old client who has been brought
in because of speech difficulty. They note
that the client is tongue-tied. The mother of
the client wants to know more about it.

a. How would the nurse describe the function of the frenulum to the mother and the complications that can occur with the tongue?

Answer 22

• On the bottom of the tongue is a fold of mucous membranes called the frenulum.
  
  • This structure helps to attach the tongue to the floor of the mouth.
• A person is said to be “tongue-tied” when the frenulum of the tongue is too short or too tightly attached. It results in speech difficulty.
  
  • This condition can be surgically corrected.

Question 23

What are the functions of the tongue?

Answer 23

• The tongue is involved in sensing the temperature and texture of foods.
• It brings the food to be chewed into position and also brings about mixing of the food with saliva.
• It commences the process of deglutition and pushes food into the pharynx.
• The presence of taste buds on the tongue helps distinguish various flavors.

Question 24

A client informs the nurse that they have been experiencing a burning sensation in the chest for 2 days. Assessment reveals heartburn.

a. What is the cause of heartburn? What is its consequence? Write a note on its treatment.

Answer 24

• Heartburn is a condition that results from inadequate closure of the lower esophageal sphincter.
• This allows the gastric contents to reenter the esophagus.
• Gastric contents, being acidic, produce a burning sensation.
• Continuous acid reflux can produce gastric or esophageal ulcers.
• This can be treated with medication and also with certain specific lifestyle changes.

Question 25

What is the function of the lower esophageal sphincter (LES)?

Answer 25

* The LES is located on the lower end of the esophagus. * Relaxation of the LES allows food to enter the stomach. * The LES guards the opening of the gastric fundus and prevents the reflux of food into the esophagus.

Question 26

What are the various functions of the liver that the nurse needs to know to help explain the pathology of the liver to a client?

Answer 26

The liver plays a pivotal role in all the body functions. The functions of liver include: * Absorption of bilirubin from old and destroyed red blood cells * Detoxification of the blood * Storage of fat-soluble vitamins (A, D, E, K) and iron * Storage of B complex, minerals, fat, and glycogen * Formation of plasma proteins and vitamin A * Formation of triglycerides and cholesterol * Production of urea, clotting factors, and immunoglobulin * Secretion of bile and heparin * Production of body heat * Storage of glucose in the form of glycogen

Question 27

A nurse is assessing an older adult client who complains of constipation. What are the effects of aging on the digestive system that a nurse needs to know in treating such a client?

Answer 27

The effects of aging on the digestive system, which result in constipation, include the following: * Poor and inadequate intake of food can result from loss of teeth due to accident or gum disease, ill-fitting dentures, decreased chewing and swallowing ability, or the lack of appreciation of taste. * There is an impairment of the secretion of the digestive juices. * Food tends to stay much longer in the stomach. * Peristalsis slows down. * There is reduced absorption due to reduction in the size of villi. * Often there is inadequate fluid intake. * Often there is inadequate daily exercise.